Heretofore, a semiconductor module and a cooler thereof are formed in the following way.
FIGS. 5(a)-5(c) are diagrams with a heretofore known semiconductor module 500a mounted on a cooler 500b, wherein FIG. 5(a) shows a main portion plan view, viewed through a bottom plate of the cooler from the rear, FIG. 5(b) shows a main portion sectional view taken along line 5(b)-5(b) in FIG. 5(a), and FIG. 5(c) shows a main portion sectional view taken along the line 5(c)-5(c) in FIG. 5(a).
The semiconductor module 500a includes a metal base 51, six circuit substrates 54 each having an insulating substrate 54a, a circuit portion 54b on the front surface of the insulating substrate 54a, and a metal portion 54c on the rear surface of the insulating substrate 54a, and a plurality of semiconductor chips 58, each being firmly fixed to each circuit portion 54b. The semiconductor module 500a includes first external terminals 59a each being connected to each semiconductor chip 58, second external terminals 59b each being connected to each circuit portion 54b, and a resin portion 60 sealing the whole with the rear surface of the metal base 51, leading end portions of the first external terminals 59a, and leading end portions of the second external terminals 59c being exposed. One wherein the circuit substrate 54, to which the semiconductor chip 58 is firmly fixed, the first external terminal 59a, and the second external terminal 59b are assembled by a joining material, such as a solder, is called an intermediate assembly 52. Herein, a case in which six intermediate assemblies 52 are mounted is shown. Normally, each of the intermediate assemblies 52 includes, for example, an IGBT (insulated gate bipolar transistor) chip and an FWD (free wheeling diode) chip connected in inverse parallel thereto.
The cooler 500b includes a top plate 70, a jacket 71 fixed to the top plate 70, and fins 72, disposed in the jacket 71, which are disposed parallel to the stream of cooling water and firmly fixed to the top plate 70. The jacket 71 is an open-topped casing having a side plate 71a and bottom plate 71b, and a refrigerant inflow port 73 and a refrigerant outflow port 74 are provided in the side plate 71a. The fins 72 are disposed uniformly in parallel in the jacket 71, and the fins 72 have a flat shape. Each intermediate assembly 52 is cooled by flowing a refrigerant between adjacent fins 72.
A semiconductor device 500 is formed of the semiconductor module 500a and the cooler 500b, wherein for example, a thermal compound 78 is applied to the metal base 51 of the semiconductor module 500a, and the semiconductor module 500a is fixed to the cooler 500b by bolts, bands, or the like.
Herein, the cooling of the semiconductor module 500a on which is mounted the plurality of semiconductor chips 58 is carried out by one cooler 500b, and the control of the cooling capacity of the cooler 500b is carried out by adjusting the flow rate of the refrigerant.
For example, PTL 1 describes a heat sink wherein cooling fins having a bimetal structure, with two metals of each fin warping in opposite directions to each other depending on temperature, increase surface area, thus improving the cooling capacity.
Also, PTL 2 describes a cooing device wherein heat is transferred to a bimetal from an uncooled body by a heat pipe, and a flap is formed by a change in shape of the bimetal, thus changing the volume of cooling air.
Also, PTL 3 describes a semiconductor device cooling device which transfers heat generated from each semiconductor chip of a multichip module with a substrate to which a plurality of semiconductor chips is firmly fixed, to a cooling jacket provided opposite the module, and thus collectively cooling the semiconductor chips for each module, wherein the temperatures of the semiconductor chips on the substrate are individually detected, and the coolings of the semiconductor chips are individually controlled based on the detected temperatures.